During archeological research in Pompeii a set of Roman tokens – spintria – was found, usually depicting sexual acts or symbols:
Spintriae from Pompeii
There were usually struck from brass or bronze, and were little smaller than a U.S. quarter. Spintriae may have been used to pay prostitute, who at times spoke a different language. While this is subject to argument, the numbers on them line up with known prices for Roman prostitutes. Some theorize them gaming tokens, and they may have been produced for only a short period, probably in the 1st century A.D.
Spintriae are a popular target of collecting and depending on the condition have a high auction price. Because of its relevance to the numismatic market, beware of huge modern forgery.
See more spintriae in details.